The goal objective of this research is to elucidate the mechanisms underlying the control of keratinocyte growth and gene expression in oral epithelial tissues, and to assess how these processes are altered in oral cancers. To achieve this goal, we are focusing on understanding the regulatory controls that govern the genes that encode keratins, the major structural proteins of oral epithelial cells. This understanding will not only be useful to our understanding of how malignancy leads to aberrations in gene control, but in addition, the keratin promoters will be valuable for developing keratinocytes as a vehicle for gene therapy in the treatment of premalignant and/or postoperative head and neck Cancers. The 5' sequences of K14 and K5 are sufficient to faithfully drive expression in the mitotically active keratinocytes of tongue, buccal and tooth epithelia of transgenic mice. Due to their enormous proliferative capacity in culture, keratinocytes have been used successfully for bum operations and are potentially powerful vehicles for drug delivery and gene therapy of oral cancers and other tissue abnormalities. Elucidating how K5 and K14 promoter activity is controlled will be key in developing keratinocytes for these purposes. To this end, we will identify the critical sequences and factors that are central to efficient expression of foreign genes in oral keratinocytes. We will also explore how these factors are themselves regulated, and whether these processes are altered in oral squamous cell carcinomas (SQCCs). We will also explore how retinoids control differentiation in normal and SQCC keratinocytes, and elucidate the key retinoid receptor mediated target genes involved in this process. Such work is particularly important to developing new and improved retinoids for the treatment of oral leukoplakias caused by heavy smoking. We are also interested in identifying the critical molecular differences that distinguish a mitotically active oral keratinocyte from a leukoplakia keratinocyte and from an SQCC keratinocyte. We have devised a strategy to screen for such differences, and to test their importance by examining premalignant and malignant tissues in vivo. Finally, using transgenic mouse technology, embryonic stem cell technology and conditional knockouts with oral keratinocyte promoters, we will engineer in mice the molecular aberrations that we detect in the keratinocytes of oral cancers. These studies will not only allow us to assess the functional significance of such aberrations and their role in tumor progression, but in addition will provide valuable animal models for developing new and improved tools for the-diagnosis and treatment of these cancers. Our laboratory has recently pioneered research that illustrates how an understanding of keratinocyte biology can lead us to the causes of a variety of human genetic disorders. In the coming years, we will continue our endeavors to apply our molecular genetic research to medicine.